Stator construction for axial-flow fluid machine



May 27, 1958 N. E. PAYNE ETAL 2,836,393

vS'I'ATOR CONSTRUCTION FOR AXIAL-FLOW FLUID MACHINE Filed July 19, 19562 Sheets-Sheet 1 Z2 Z1 Z g' 16 K 20 19 160/ 1% fifl 15 if Y 34 May 27,1958 N. E. PAYNE ET AL 2,836,393

STATOR CONSTRUCTION FOR AXIAL-FLOW FLUID MACHINE Filed July 19, 1956 2Sheets-Sheet 2 Fig.6..

Unite rates Patent STATOR CGNSTRUCTION FOR AXIAL-FLOW FLUID MACHINENigel Edward Payne, Burton-on-Trent, and Frederick Freeman, Derby,England, assignors to Rolls-Royce This invention relates to axial-flowfluid machines such as turbines or compressors of gas-turbine engines.

This invention has for an object to provide a construction of statorwith hollow blades showing advantages in manufacture and operation.

According to the present invention, a stator of an axialflow fluid.machine comprises a ring of hollow stator blades secured at their innerand outer ends in hollow, box-like inner and outer blade platformstructures, the passages through the blades opening into the interiorsof the box-like platform structures, an outer casing structure whereinthe blades are mounted through the outer platform structures, first ductconnections connecting the interiors of the outer platform structures toexternally of the outer casing structure, and second duct connectionsconnecting the interiors of the inner platform structures to a chamberwithin internal stationary structure of the engine.

The construction of this invention enables low-pressure air to be passedthrough the blades, say for cooling, as compared with high-pressure airusually employed hitherto, the air flowing either from a low-pressurechamber internally of the engine to externally of the outer casingstructure, or in the reverse direction; a more efiicient operation ofthe fluid machine is thus achieved.

The blades may have individual inner and outer platform structures, butpreferably the blades are arranged in a plurality of sets, there beingsay three blades in a set, and the blades of a set have common inner andouter platform structures which act as manifolds for distributing air toand collecting air from the blades of the set. Such a blade and platformarrangement improves the loadbearing capacity of the structure, and atthe same time reduces the number of duct connections and the number ofports necessary in the outer casing structure as compared withconstructions in which each blade has individual platform structures.

In one preferred construction, the radially outer walls of the commonouter platform structures and the outer casing structure have portstherein formed by hollow bosses, and tubular plugs engage by their endsin the bores to connect the interiors of the outer platform structuresto externally of the outer casing structure, and the common innerplatform structures have ports to their interiors formed by hollowradial bosses on their radially inner walls to engage plug-wise inradial sockets provided on a wall of the chamber and opening into thechamber. In this case, the socket-engaging bosses may also be employedto locate internal engine structure coaxially within the ring of statorblades.

There will now be described a gas turbine having nozzle guide vanes atthe entry of the turbine constructed in accordance with this invention.The description refers to the accompanying drawings in which- Figure 1is a part axial section through the turbine,

Figure 2 is a section on the line II-II of Figure 1,

Figure 3 is an axial section through a modified construction, and

Figure 4 is a section on the line IVIV of Figure 3.

Referring to the drawings, the turbine comprises a rotor having a shaft10 which has secured to one end thereof a turbine disc 11 with a ring ofrotor blades 12 mounted on its periphery. The turbine also comprises astator having an outer load-bearing casing structure 13 from which issupported a ring of nozzle guide vanes 14 through the passages betweenwhich hot gas from cornbustion equipment 15 flows to be directed ontothe rotor blades 12, and the nozzle guide vanes 14 in turn support abearing 16 for the downstream end of the turbine shaft 10.

The nozzle guide vanes 14 which are hollow are arranged in sets of three(see Figure 2) and each set of three nozzle guide vanes 14 hasassociated with it a hollow, box-like inner platform structure and ahollow boxlike outer platform structure.

The outer platform structure of each set of vanes comprises a plate 17having slots in which the outer ends of the vanes are secured as bywelding or brazing and the plate 17 forms a portion of the wall of theworking fiuid annulus of the turbine. The plate 17 is secured to flanges18a around the edges of an outer wall part 18 so that the plate 17 is inspaced relation to the outer wall part 18 and so that a manifold space19 is formed into which open the outer ends of the passages through thevanes 14. The outer wall part 18 of the outer platform. structure hasformed integrally with it a hollow boss 20, the bore of which opens intothe manifold space 19 and forms a socket to receive one end of a tubularplug 21, the opposite end of which is engaged in a socket formed by ahollow boss 22 provided on the outer casing structure 13 and forming aport opening through the outer casing structure to atmosphere. A crosspin 23 is fitted in the boss 22 to prevent the disengagement of the plug21. The plug 21 has part-spherical end portions by which it engages thebores of the hollow bosses 20 and 22.

The outer wall part 18 is also provided externally withoutwardly-extending dogs 24 at axially-spaced points to co-operate withcorresponding dogs 25 on the outer casing structure 13 so as to locatethe outer platform structure circumferentially in the turbine. The outerwall part 18 also is provided with a thickened edge 26 at its downstreamend, which edge is provided with an axially-facing groove to receive theupstream edge of a shroud ring 27 for the turbine rotor blades 12-. Theshroud ring 27 is located both axially and circumferentially withrespect to the outer casing structure 13. Since the gas loads on thevanes 14 tend to displace the vanes downstream, the shroud ring 27 alsoserves to locate the vanes axially.

The inner platform structure associated with a set of vanes comprises aplate 28 which has an inward flange at its upstream edge and also isformed with slots in which the inner ends of the vanes 14 are secured asby welding or brazing. The plate 28 forms a portion of the inner wall ofthe working fluid annulus of the turbine. The inner platform structurealso comprises an inner Wall part 29 having flanges 29:: along itscircumferentially spaced edges and its downstream edges and the plate 23is secured to the flanges 29a, so that the plate 28 is spaced from thewall 29 and forms a manifold space 30 into which open the inner ends ofthe passages in the vanes 14.

Theinner wall part 2 9 has formed integrally with it a hollow boss 31which forms the plug of a plug and socket duct connection between themanifold space 30 of the inner platform structure and an annular chamber47 formed in a support for the bearing 16.

The bearing support comprises an upstream radiallyextending annulardiaphragm 32, a downstream radiallyextending annular diaphragm 33 and anannular rim member 34. The rim member 34 is formed with a number ofhollow bosses 35 which form the sockets to receive the plugs 31 and itis also formed with a number of swellings 36 the purpose of which willappear below.

v The diaphragms 32, 33 at their outer perioheries lie against theupstream and downstream faces of the rim member 3 4 and are held inposition by upstream and downstream clamping rings 37, 33 and by boltswhich pass through the clamping rings, the peripheries of the'diaphragrns 32, 33 and the swellings 36 of the rim member34. ,7

V J At an inner radius the diaphragms as,

with axial flanges 3?, which abut one another and an "A as are providedhold the diaphragms 32, 33 in axially-spaced relation at this radiusvThe diaphragm 3?. is also provided 'internally with aradially-inwardly-extending fiange 41 1 having atits free edge a spiinedaxial extension 42 which receives the splined outer race 16a of thebearing 16.

v The clamping rings 37, 38 not only serve to hold the diaphragms 32, 33against the rim member 34 but also serve to locate the inner ends of thenozzle guide vanes 14 opensthe outer end of the passage through theassociated lade.

The pans 118 are formed each with a hollow boss 12%"? wherein is engagedone end of a tubular plug 121,

the opposite end being engagedin a corresponding hollow boss 122 on theouter casingstructure 313.

The parts ill also have outwardly extending ribs 124 which form dogs toengage between corresponding dog s 125011 the casing structure 13 tolocate the outer platform structure in position.

ing, a ring of stator blades extending radially between with respect toone another and for this purpose the clamping ring 37 is provided with aflange portion 43 with an axially-facing annular'slot to receive axialproj'ections at the upstream edgesof'the inner wall parts 23 and theclamping ring 33 is providedwith an axial flange 45 having therein anaxially-facing annular slot to receive projections 45mm the downstreamedges of the inner wall parts 2 V The annular chamber 47 is 32, 33,flanges 39, 49 and the rim member 34, and the chamber is used as acollector manifold for low-pressure air to be conveyed through thehollow nozzle guide vanes 14 to atmosphere. The air may be low-pressureair which leaks into space 5i) adjacent the compressor, say through acompressor rotor seal, and this air may pass into the chamber 47 throughholes 51 in the diaphragm 32. Alternatively or in addition, the air maybelow-pressure cooling air tapped oli from a low-pressure stage of theengine compressor and conveyed through the shaft 16 to flow throughports 2 therein adjacent bearing 16 into space 53 and thence throughrotating'seal 55 which acts as a flow restrictor to space 56. The airthen flows through ports 54 in flange 4% from space se to the chamber47. The air flows'outwardly from the annular chamber 47 through theducts formed by the hollow "bosses 35 and the hollow plugs 31 into themanifold spaces 31} in the inner platform structures, and then flowsoutwardly through the hollow nozzle guide vanes 14 into the manifoldspaces 19 of the outer platform structures and from thence to atmospherethrough ducts aflorded by the tubular plugs 21. v

Since the air is low-pressure air, the mass flow of air.

is less than when the air is high-pressure air, and consequently theengine operates more elhcicntly because less energy is absorbed in theengine in compressing the air specifically tapped for cooling or becausethe cooling air is leakage air.

It will be noted also that the vanes 14 and their platform structuresare of simple construction yet are capable of withstanding heavy loads.Also, the vane structure assists through the bosses 31, 35 incentralising the bearing'l'fv.

In another arrangement (Figures 3 and'4), instead or" outer wall part118 thus definesa space 119 into which bounded by the diaphragms saidannular structure and said stator casing, each of 7 said stator bladeshaving a passage extending through it and opening/through each end ofthe blade, means connecting the stator' blades with the annularstructure, said means comprising a series of part-annular inner hollowstructures between the inner ends of the blades andfsaid annularstructure, each of said part-annular inner hollow structures subtendingat the axis of the machine an angle equal to the angle subtended at theaxis by a plurality of'said stator blades, each of saidpart-annular'inner 'hollow structures having radially-spaced inner andouter walls,'the outer wall having in it a number of slots equal innumber'to said plurality of the stator blades and each of said slotshaving the inner end of a cor'respondin'g one of the plurality of statorblades rigidly secured therein whereby the passages in said plurality ofthe stator bladesopen .to the space between said inner and outer walls,each of said inner hollow structures having a single duct connectionextendingradially-inwardly from its inner wall to the outer annular partand connecting said. space between the inner and outer walls of theinner hollow structure and the annularchamber, and said series of innerhollow structures together defining a complete annulus, and meansconnecting the stator blades with the stator casing, said meanscomprising a second series of outer hollow structures which togetherform a complete annulus radially between the stator casing and thedially outer ends of thetstator blades being rigidly securediin saidslots whereby the outer ends of the passages v in the;stat0r blades openinto the spaces between the walls of the outer hollow structures, aplurality of angularly-spaced pressurefluid connections externally ofsaid stator casing, the number of said pressure fluid connections beingequal to the number of outer hollow structures, and a singlefductconnection extending radially outwards from the outer walltof each ofsaid outer hollow structuresrto a corresponding one of said pressurefluid connnections. V

, 2, An axial-flow fluid machine according to claim 1, wherein thenumber of said outer hollow structures is equalj to the number of saidinner hollow structures, the inner'wall of each outer hollow structurehas therein a number of blade-receiving slots equal to the number ofblades-in said'plurality of the stator blades, and the' blades which aresecured in'the outer 'wall of each inner hollowstructure, have theirouter ends secured in the slots in the inner wall of a corresponding oneof the 5 comprises a number of radially-outwardly-extending socketsequal to the number of inner hollow structures, and the inner wall ofeach inner hollow structure having formed thereon a hollow radial bossengaging plugwise within a corresponding one of said sockets, the ductconnection between the inner hollow structure and the chamber beingaflorded by said hollow boss and said socket.

5. An axial-flow fluid machine according to claim 1, wherein saidannular structure comprises a pair of axially-spaced annular diaphragms,said outer annular part being between said diaphragms adjacent theirperipheries and holding them in spaced relation, axial flanges on saiddiaphragms adjacent their inner peripheries, the axial flanges abuttingone another and affording a radiallyinner wall of said annular chamberand clamping means extending through said diaphragms and the outerannular part and holding them in axial abutment, said clamping meansalso engaging the inner hollow structure and locating them radially withrespect to one another.

6. An axial-flow fluid machine according to claim 5, comprising also arotor, a bearing for the rotor, said 6 bearing having an outerstationary race, said race being supported by one of said diaphragrns atits inner periphery.

7. An axial-flow fluid machine according to claim 1, wherein each ofsaid duct connections extending outwardly from the outer wall of each ofsaid outer hollow structures comprises a hollow boss extending radiallyoutwards from said outer wall, a hollow boss extending outwards fromsaid stator casing, and a tubular plug member having one end engaged inthe hollow boss on said outer wall and its opposite end engaging thehollow boss on the stator casing, the tubular plug having its endspart-spherical.

References (Iited in the file of this patent UNITED STATES PATENTSWislicensus June 2, 1953 Wilkinson Mar. 20, 1956 Hunter Apr. 10, 1956

